function cw() {
  var a = document.getElementsByClassName('m');
  var b = a[0]['innerHTML'];
  var s = a[1]['innerHTML'];
  alert(b+s);
}
// 注释

var a;
a = 1;
var b ='2';
var c = a+b;
console.log(c);
var d = parseInt('3');
console.log(d);
a+=2; // a=a+2;

if(a===2){

}
switch (a) {
  case 1:
    a+= 1;
    break;
  case 2:
    a-=1;
    break;
}
